It doesn't matter how many pictures you take, you will always need more. So go crazy with the camera. I usually start at the plunger and go around the machine counterclockwise. I do this for each "layer" I encounter. Each time I take something off, I photo it as well, and pay attention to the type of screw, post, etc. with a picture of it next to its place on the playfield. I organize in plastic zip locks, and just write on the bag with a sharpie.
I keep a running list of parts I need.
I do not re-solder, unless there is a bad connection or reason to do so.
For the underside, I label everything with a number, with a corresponding number on the playfield, with a sharpie. So hole 27 takes the GI socket that I put a 27 on, etc. For some things, like transistor boards or switches, I'll outline them with the sharpie as well as number them. Once I have everything disconnected, with lots of photos, I slide the wiring harness onto a large piece of cardboard, labeling head and foot. Putting the wiring harness back then just requires sliding it onto the playfield underside, and screwing things back in place in reverse numerical order. Obviously I clean everything and replace/resolder connections as necessary.
Underside things like rollover switch brackets and such can be photographed once the wiring harness is off and put in plastic bags as well.
This is a huge project. Don't count on things being disconnected just a few days. It'll be months, if you are a hobbyist with other family responsibilities, before you reconnect that last plastic or put on that last rubber ring. Document in a way that someone who wasn't present when it was taken apart could use the documentation to put it back together.